3-Acylhydrazonomethyl rifamycins

ABSTRACT

WHEREIN R and X have the same meaning as before, and R5 may be the same as R1 under (a), (b) or (c) as given above or it may further represent a -CO-NH-NH2 or a -(R4)-CO-NH-NH2 group wherein R4 has the same meaning as before; or R and R5 taken together may also represent a carbocyclic chain forming with the adjacent -NX-group a 5- to 7-membered heterocyclic ring fused with a benzene nucleus. The compounds have antimicrobial activity.   The compounds are prepared by reacting at a water-liberating temperature 3-formylrifamycin SV or its 25-desacetyl or the corresponding hexahydro derivative in a suitable organic solvent with a substantially equimolar amount of a substituted hydrazine of the formula   and 25-desacetyl and 16, 17; 18, 19; 28, 29-hexahydro derivatives thereof in which X is a -CO-, -CS-, -C(:NH)- or -SO2group, Me is a methyl group, R is hydrogen, R1 is a member of the group consisting of (a) alkyl, alkoxy, aryl and aralkyl groups; (b) an -NR2R3 group wherein R2 and R3 are independently selected from the group of hydrogen, C1-C6 lower alkyl, C3-C6 lower alkenyl, nitro and anilino groups; (c) a -CO-NH-N CH-A or a -(R4)-CO-NH-N CH-A group, wherein R4 is a divalent aliphatic, cycloaliphatic, aromatic or heterocyclic group and A represents the rifamycin SV group:   3-Acylhydrazonomethyl rifamycin SV derivatives, of formula (I)

nited States Patent [1 1 tCric-chio et al.

{45H Feb. 11, 1975 3-ACYLHYDRAZONOMETHYL RHFAMYCINS [75] inventors: Renato Cricchio, Varese; Giancarlo Lancini, Pavia, both of Italy [73] Assignee: (Eruppo Lepetit S. p,A., Milan Italy [22] Filed: Mar. 16, 1973 [21] Appl. No.: 342,047

[30] Foreign Application Priority Data Primary Examiner-Henry R. Jiles Assistant ExaminerRobert T. Bond Attorney, Agent, or FirmTheodore Post; C. Kenneth Bjork [57] ABSTRACT 3-Acylhydrazonomethyl rifamycin SV derivatives, of

formula (l) and 25-desacetyl and l6, l7; l8, 19; 28, 29-hexahydro derivatives thereof in which X is a CO, CS, C(:NH) or SO group, Me is a methyl group, R is hydrogen, R is a member of the group consisting of (a) alkyl, alkoxy. aryl and ar'alkyl groups; (b) an NR R group wherein R and R are independently selected from the group of hydrogen, C C lower alkyl, C -C lower alkenyl. nitro and anilino groups; (c) a CO--NH-N=CH-A or a (R,)-CON- H-N=CH-A group, wherein R, is a divalent aliphatic, cycloaliphatic, aromatic or heterocyclic group and A represents the rifamycin SV group ME Me or the corresponding 25-desacetyl or l6, l7; l8, 19; 28, 29-hexahydro derivative thereof; and R and R taken together with the adjacent N-X-group may represent a 5- to 7-membered heterocyclic ring fused with a benzene nucleus.

The compounds are prepared by reacting at a water-liberating temperature 3-formylrifamycin SV or its 25-desacetyl or the corresponding hexahydro derivative in a suitable organic solvent with a substantially equimolar amount of a substituted hydrazine of the formula l H N-N-X-R wherein R and X have the same meaning as before, and R may be the same as R, under (a), (b) or (c) as given above or it may further represent a CON- H-NH or a (R )CONH-NH group wherein R has the same meaning as before; or R and R taken together may also represent a carbocyclic chain forming with the adjacent NX--group a 5- to 7- membered heterocyclic ring fused with a benzene nucleus. The compounds have antimicrobial activity.

1 Claim, No Drawings C LHYDBAZQN METHYL ...R.IEAMCENS.

BRIEF SUMMARY OF THE INVENTION This invention is concerned with 3- acylhydrazonomethyl rifamycins corresponding to formula (l) Me he "if? mecoog l CEO I Me Me l MeO M NH R CH=N-NX-R or the corresponding 25-desacetyl or l6, l7; l8, I9; 28, 29-hexahydro derivative thereof; and R and R taken together with the adjacent --NX-group may represent a to 7-membered heterocyclic ring fused with a benzene nucleus.

The compounds of this invention are further characterized in that:

1. when X is a CO- group, R may not be an NH group;

2. when X is (C:NH)--, R may not be an -NH group;

3. and when X is -SO R may not be p-tolyl. The term alkyl alone or as part of a compound term such as, for instance, alkoxy, designates a straight or branched chain alkyl group having from 1 to carbon atoms. The alkyl groups may also carry one or more substituents selected from halo, nitro, cyano, hydroxy, alkoxy, oxo, carboxy, carbalkoxy, amino, acylamino,

hydroxyamino, sulfo, sulfamido and thiono. The term phenyl, amino, acylamino, hydroxyamino, mono and di-lower alkylamino, cyano, halo, nitro. l to 6 carbon lower alkoxy, methylenedioxy, sulfo, carboxy, carbalkoxy, carbamyl, sulfonamido and the like. the term cycloalkyl designates 3 to l0 carbon atom cycloalkyl groups and may also identify bridged or spyro systems. The term aralkyl" designates 'l to 6 carbon alkyl groups substituted with one or more aryl groups. When the'groups R and R, taken together with the adjacent -N-X-group form a benzo fused 5- to 7-membered heterocyclic ring and X is a CO group, the heterocyclic portion may carry as a substituent another oxo group.

The process for preparing the new compounds consists in condensing 3-formylrifamycin SV and its 25- a a- 1mm wherein R and X have the same meaning as above, and R may have the same meaning as R, under (a), (b) or (c) above or may further represent a CO-NH--NH or a (R )-CONHNH group wherein R has the same meaning as above; R and R taken together may also represent a carbocyclic chain forming with the adjacent N-X-group a 5 to 7-membered heterocyclic ring fused with a benzene nucleus. The reaction temperature is generally room temperature, but if the reac tion rate is low, the mixture may be heated to the boiling temperature of the solvent. The reaction may be followed by evolution of water of condensation. As is evident, if a derivative of formula (II) carrying two hydrazine functions is employed, the final product is an azine of 3-formylrifamycin SV of formula (I), falling within paragraph (c). r

The new compounds are colored solids which may be crystallized from common organic solvents such as, for example, lower alkanols, ethyl acetate, dioxane, tetrahydrofuran, benzene and liquid chlorinated hydrocarbons. Their solubility in organic solvents depends obviously on the nature and the size of the various substituents R, R and X. When an acidic function is present, the compounds are also soluble in water as a salt with a suitable base such as, for instance, an alkali metal base.

DESCRIPTION OF SOME PREFERRED EMBODIMENTS The following example describes the preparation of representative specific embodiments and the best mode contemplated by the inventors of carrying out the invention.

EXAMPLE To a tetrahydrofuran solution of 0.01 mole of 3-formylrifamycin SV or the 25-desacetyl derivative thereof or the corresponding l6, l7; l8, I9; 28, 29 hexahydro derivative, 0.01 mole of a substituted hydrazine of the formula H NNRXR as previously described is added at room temperature. Generally, the reaction is completed in 2 to 3 hours. In the event that a chromatographic assay on a silica-gel plate then indicates or by column chromatography. that the reaction is not completed, the mixture is refluxed for an additional -45 minutes. The reaction In the following Table l are given the chemicomixture is evaporated to dryness and the crude solid is physical data of representative compounds of formula purified by crystallization from an organic solvent, such 5 (I) prepared as described above from 3-formylritamyas, for example, methanol, ethyl acetate, or chloroform cin SV and a hydrazine derivative of formula (ll).

TABLE I Starting R R X Crystallization M.p. or Yield Sinnificant U.V. and visible bands hydrazine solvent or decompo- 17 compound chromatography sition, A max E H h H H u J,U V 1 cm. g H H 11 CS THF 180 70 l 53 3 1 7-9;3 9

H N-NH-C0-CH l 11 e11 co Methanol 17 1-7 #78534 191.1 ;33 +.3

. O 4 2m (j co A etone 188-90 480335 1593271 CH2 J0 H2N N n p 5 CO Ethyl acetate 253- 9O33 l5;3l5 l5l;306;255

ca I 1 c 2 E L a -ca oa Ethy acetate 238 60 480537 166 355 11 N-NH-O a I G H CH 2 )c 2 1) C0 Ethyl acetate 2 6-70 53 3 1595253 l 0 II I i c0 Methanol 215-7 80 U.VaSpe ctrum not carried out as the product decomposes a -CH CN co Methanol 188-90 65 480333 186 .6;315 3 H N-NH-CO-CH CN H N-NHC0 H 48 i,- 1 0-254 H C OOCI;I-CH tic-1343p co Benzene 185 7 60 337 5 0H COOC H H N-NH-CO-C=(C H a i co Benzene 1 s a0 9o +71;328 13?;237

ca on F;; 6 T H N-NH-COD i p 00 Benzene -8 75 478334 161;29o .4

H aocH H00 6 c0 H5 H C co Benzene 181-3 55 7 33 5 3 75 H nocii 3 CH O H NNH-COCH CH a -CH -CH co (gazbon 187-9 75 0333 9 ;33l

, chloride H -NH ;H -ca(ca co l flgglg g a 185-7 l -55 480 188524 l H2 H V H N-NH- I H -c 2 co E hy acetate/ 185-7 50 480;335 1976 7 CH H2 ligroin Starting R R X Crystallization M.p. or Yield Significant U.V. and hydrazine solvent or decompo- 76 visible bands 1% compound chromatography sition, E

7-8.-. r 1 H Ethyl acetate 130-33 85 488 339 l26.3;2 +2.6

H CH2CONHN=CHA H- B c0 M n l 223- 65 48063 155.9;289.7

H N-NH-COCONl-Bl'l-l H -c0mm=c1m co h ol 230 5053315 l42 9;273 l H co e z fi' g Ethyl acetate/ 230 68 9 M3 3 l3h9326h8 ligroin 0 0 c1 c1 'Q Q 2 Carlwn tetra 1 28 8033 131.6 ;221.7

1 i l chloride 3 H cn ocogu. f r H2N-NH-CO-(CH2)2('ZH-COOH -?CH2)2-'HI co Benzene 178-80 90 4 5 5; 152.9;2o5.6

C H CH OC0NH coon ll,,N--NH--CO co Methanol 17o dec. 98 488 340: 1 2 4 NH 1 N 1 A ll N-NH-COCH -CH CONHNH -(CH -COHN-N=CHAi Meirthanol/ 22o dec. 30 @9531) 6;2 g

' C0 1 gro n H N-Nll-K'IU( J=(C H H -J=(C6H5)2 co Ech 1 acetate 180- M80536 151.5;2713),

HO HO H, ll-NH-CSNHCH CH=CH l1 lm-c1i -cn=cn Methanol 265 87 4853 451 92 ll N-NH-CSNH H NH-C6H5 cs Methanol 230 dec. 96 1 4 1 8 The microanalytical data of all compounds listed above are in agreement with the calculated values.

The microanalytical data of all compounds listed above TABLE II are in agreement with the calculated values. Pursuant to the described method, hydrazones of 3-f0r- R R X mylrifamycin SV, ZS-desacetylrifamycin SV and their Md 7 hexahydro derivatives are prepared by condensing l them with the following hydrazine derivatives: 40 H CO 2 TABLE II HN' ia-T12 H CO R R X 00 115 a NO 00 H 0 11 CO H H Q-Br co CH OH H CH CO 3 N0 OCH H Q 00 0 CO NH H OH C 3 H HCOCH CO OH OCH H 3 H 00 H CO HO CH3 10 v TABLE II cont.

TABLE II cont.

2 2 2 2 2 2 2 2 2 2 O S O O O O O O S S O 0 0 w "w Q U w m Q Q S S S C C C W C C C C C C C 7 M 3 3 1 r 3 w a r O B 2 2 m w a m l H 0 B S O H 0 1 l 3 C C 2 N 1 3 N 5 C C 3 3 \.I H l H h 0 H 3 C \1 l C H m H H 0 W C C H H H MW 6 O N m m M M /l\ N l C 5 m U m E w M m M w 5 w 6 M UN H O O O O O N O 0 O 0 O O O W w W C n w m C C C C C C C C C C C C C W. 2 C 3 3 O w O F l l C C C 2 w C I 9 20 To b, w h 0 C "w M: 2 2 C 0.. C a V. H n w n v w 10k m H O o 2 v d C H H C a 2 2 2 H H H C C C H H H H H H H H H H H H H H H H H H The compounds of the invention have a remarkable antibacterial activity against Gram-positive and Gramnegative bacteria. In particular, the new compounds display a remarkable activity against S. aureus strains. In this case the mineral inhibitory concentration varies from about 0.001 to about 0.05 ug/ml. The compounds are active also against microorganisms resistant to other known and widely used antibiotic substances.

1n representative experiments on mice, amounts ranging from about 1 mg/kg. to about 5 mg/kg. p.o. proved highly effective in inhibiting the experimental infection from S. aureus. In other experiments, representative compounds of the invention proved to be active at doses of about 1-5 ,ug/ml. also against S. aureus Tour strains resistant to other rifamycins usually employed in therapeutic practice. The toxicities of the new compounds are very low and vary from about 250 to about 1,500 mg/kg. i.v. in mice.

Another very important feature of the invention compounds is their inhibiting activity of DNA polymerases which are characteristics of human leukemic blood lymphoblasts and against typical nucleotidyl transferases (polymerases) of viruses not utilized by the normal cell. It is known from studies on representative members of virus groups that they either carry or induce in the host cells polymerases as an essential part of their replication. Thus, there are viruses such as picornaviruses or polioviruses which induce RNA- dependent RNA-polymerase while other groups such as leukemia-sarcoma viruses carry an RNA-dependent DNA-polymerase. The presence and the very important role of the RNA-dependent DNA-polymerase (reverse transcriptase) in oncogenic RNA viruses has been discovered by D. Baltimore, Nature, 226, 1209, (1970) and by H. M. Temin et al., Nature, 226, 1211 (1970). Recent discovery of RNA-dependent DNA- polymerase enzyme in RNA tumor viruses of animal species has been confirmed by other researchers, as the following papers show:

Green et 2112 Mechanism of carcinogenesis by RNA tumor viruses, 1. An RNA-dependent DNA-polymerase in murine sarcoma viruses. Proc. Nat. Acad. Sci. USA 67, 385-393, 1970.

Spiege'lmatiiet a1: Characterization of the products of RNA direct DNA-polymerases in oncogenic RNA viruses, Nature, London, 227, 563, 1970.

with RNA tumor viruses. Proc. Nat. Acad. Sci. USA,

' tumor viruses. Proc. Nat. Acad. Sci. USA, 67. 1034,

RNA virus implication in some tumors has been supported also by other facts: reverse transcriptase has been found to be present in particles from human milk obtained from women with a familiar history of breast cancer and from inbred population. (Scholn et al.: Nature, 231, 97, 1971). Priori etal. (Nature New Biology, 232, 16, 1971) isolated a virus named ESP-1 contain ing reverse transcriptase from cells from the pleural fluid of a child with lymphoma and have successfully grown it in tissue cultures. The presence in human breast cancer of RNA homologous to mouse mammary tumor virus RNA has been demonstrated through molecular hybridization experiments by R. Axel et al. (Nature, 235, 32, 1972). The possibility of a human breast cancer virus was also supported by electron microscopy of human milk (N. H. Sarkar et al., Nature, 236, 103, 1972). RNA-directed DNA-polymerase activity and virus like particles have been isolated also from human rhabdomyosarcoma cells (McAllister et al., Nature, New Biol., 235, 3, 1972).

At the present there are no very effective drugs for treating viral diseases, since viruses and cells have common metabolic requirements and pathways. The most promising approach to viral chemotherapy clearly is the design of suitable chemicals which combine specifically with viral or virus-transformed cell polymerases controlling the expression of genetic information of viruses.

Specific inhibitors of the viral or virus-transformed cell enzymes and, in particular, inhibitors of polymerases of RNA tumor viruses may have an important role in providing drugs for leukemia and other cancer therapy.

The inhibiting activity of the inventive compounds has been tested on RNA-dependent DNA-polymerase of endogenous murine sarcoma virus and DNA- dependent DNA-polymerase activity of purified enzymes (poly d A-Tas template). The inhibition was tested according to the methods described by C. Gurgo et al., Nature, New Biology, 229, 111, 1971. The effect of different concentrations of drugs on polymerase activity was determined by following H TTP (tritiated thymine deoxyriboside triphosphate) incorporation into the insoluble fraction. A typical example of the experimental procedures is the following:

1. Isolation of virus and purification of viral polymerase Virus was isolated and purified from murine sarcoma virus (Moloney isolate) transformed rat cells (78Al cells) and murine sarcoma virus (Harvey isolate) transformed mouse cells (MEH cells) as previously described (M. Green et al., Proc. Nat. Acad. Sci. USA, 67, 385-393, 1970; Rokutanda et al., Nature, 227, 1,026-1,028, 1970). The virion polymerase was purifled 20-40 fold by incubation of purified virus with 0.5% NP-40 (nonidet P-40) in 0.1 M NaCl, 0.01 M Tris buffer (pH 7.6), 0.001 M EDTA for 5 minutes at room temperature and zonal centrifugation in 15-30% sucrose gradients in 10 mM sodium phosphate buffer (pH 7.4), 2.5 mM MgC1 10 mM dithiothreitol, and 5% glycerol for 24 hours at 38,000 rpm in a Spinco SW 41 rotor. The peak fractions of enzyme activity (13-17) of 22 fractions collected, were pooled, and stored at -C. in 30% glycerol.

DNA polymerase assay Enzyme incubation was performed for 1 hour at l3 37C. in 100 pl of reaction mixture containing 40 mM Tris buffer (pH 8.0), 5 mM dithiothreitol, 30 mM NaCl, 2.5 mM MgCl 0.1 mM dATP, dGTP, dCTP, and pCi of H-dTTP (12-18 Ci/mmole) as described by Green et al., in Proc. Nat. Acad. Sci. US 67, 385-393, 1970. The reaction was terminated by the addition of 150 pl of 1N perchloric acid. Calf thymus DNA (100 pg) was added as carrier; the radioactive DNA product was processed as described in the two papers mentioned above. Endogenous RNA-dependent DNA-polymerase activity was measured after the addition of 0.01% NP-4O to purified virus at the time of assay. The DNA-polymerase activity of purified viral polymerase was measured with 2pg of poly d(A-T) as template and no NP-40. Test for inhibition by 3-acylhydrazonomethyl rifamycin SV derivatives 3-Acylhydrazonomethyl rifamycin SV derivatives were dissolved in dimethyl sulfoxide (DMSO) at a concentration of 5 mg/ml and stored at 4C. Inhibition of the endogenous RNA-dependent DNA-polymerase activity was tested by adding 2 pl of derivative appropriately diluted .in DMSO or 2 pl of DMSO (control) to the assay mixture prior to addition to disrupted virus which contained 15 to 30 pg of viral protein.

Enzyme incubation was performed for 60 minutes at 37C. Inhibition of purified enzyme was tested by preincubation of 2 pl of derivative or DMSO with 30 pl of enzyme (1 to 2 pg of protein) for 10 minutes at 37C.; then 70 pl of substrate mixture were added and the mixture further incubated and processed as described above.

In representative tests, the inventive compounds at a concentration of 2-100 pg/ml or less reduced the incorporation of H-dTTP to less than 10 percent of that found in the control tests, clearly demonstrating inhibition of the mechanism of carcinogenesis by RNA tumor viruses, according to the most recent biochemical points of view.

The inhibiting effect of reverse transcriptases has been confirmed also be tests on polymerase from murine leukemia virus. Murine leukemia virus RNA- dependent DNA-polymerase was prepared from Triton X 100 disrupted virions as described by Gallo et al. in Nature, New Biology, 232, 141, (1971). Viruses of both Rauscher and Moloney types were previously purified by banding in the 1.16 g/ml region of a sucrose 1 density gradient after initial low speed centrifugation to remove cellular debris and cushioning on 60% sucrose through sucrose. Final concentration of virus preparation was at '10 particles/ml. At template, endogenous 70S RNA was used. Concentrations of 50 pg/ml or less were found to be effective in inhibiting the enzyme. Similar results were found by using tumor cell polymerases of human origin. In this case, the inhibiting activity was studied also on normal cell polymerases to characterize a selective effect. Representative rifamycin derivatives of formula (1) have been evaluated for their effects on two purified DNA- polymerases isolated from (1) human normal (PHA- stimulated) blood lymphocytes, (2) a lymphoblast cell line (derived from a normal donor) and (3) human leukemic blood lymphoblast. Synthetic and/or native templates were used.

A typical example of the experimental procedure is the following: Human Blood Lymphoblasts Leukemie lymphoblasts were isolated from the peripheral blood of patients with acute lymphocytic leukemia (All) by leukophoresis. The cells were washed and erythrocytes removed by hypotonic lysis.

Normal lymphocytes were obtained from the peripheral blood from healthy donors'after removal of granulocytes by nylon column chromatography/They were stimulated with phytohemagglutinin (PHA) for 72 hours as described before (Gallo et al., Nature, 228, 927, I970; Gallo et al., Science, 165, 400, 1968) in order to maximize DNA-polymerase activity. However, because of the logistics problem in obtaining sufficient amounts of these cells, a human normal tissue culture cell line (1788) was used to supply less purified DNA-polymerases for some of the initial survey studies. Compounds of. interest were then studied in more detail with the more purified enzymes from the normal and leukemic blood lymphocytes. These tissue culture cells were obtained from Associated Biomedic Systems, Inc.

DNA Polymerase Preparations Cellular DNA polymerases were extracted and purified from normal blood (PHA stimulated) lymphocytes, and leukemic blood lymphocytes and (1788) lymphoid cells by homogenization in hypotonic buffer followed by Triton X 100 and/or high salt extraction of the extralysosomal pellet. After differential centrifugation, cellular extracts were further purified by DEAE cellulose, phosphocellulose, and Sephadex G200 col umn chromatography.

DNA Polymerase Assays DNA polymerase assays were carried out in a final volume of 100 pl. The assay mixture contained Tris- HCl buffer, pH 8.3, 50 mM; MgAc 6.0 mM; dithiothrcitol, 8.0 mM; NaC'l, 60 mM.

Adjustment of pH was carried out after addition of inhibitors which were previously dissolved in DMSO. The final concentration of DMSO was 0.5% and all control samples included this amount ofDMSO. An enzyme concentration that catalyzes an incorporation of approximately 1.0 pmole/hr was used in the assay. The enzyme was in most cases pre-incubated for 5 minutes with the inhibitor. The reaction was then initiated by the addition of template, either synthetic DNA (poly d(AT) Miles Lab.) and DNA.RNA hybrid (oligo dT. poly rA), at 5 pg/ml or native templates: activated salmon sperm DNA at 50 pg/ml, and endogenous S viral RNA; 10 pCi of (H-methyU-TTP (New England Nuclear, 18.6 mCi/pmole, lyophilized and redissolved in 0.01 M HCljust prior to usage) and dATP (8 X 10 M, with synthetic template) or all three deoxynucleoside triphosphates (8 X l0' M with RNA or DNA templated reactions). In some experiments, there was no pre-incubation of enzyme with inhibitor. In these cases reactions were initiated by adding enzyme to the complete reaction mixture which included the inhibitor. Samples were withdrawn at the start of incubation and after 30 minutes and terminated by the addition of 2 ml. of 0.08 M sodium pyrophosphate, and precipitated in 12.5% cold trichloroaeetic acid (TCA) with yeast RNA (400 pg) as carrier. The products were collected on a Millipore filter, washed extensively with 5% TCA and 1 ml. of DMSO-ethanol-0.l M NaCl mixture (05:70:29.5), dried and counted in 2 ml. of BBS (Beckman) and 10 ml. ofliquifluor (New England Nuclear) in a Packard liquid scintillation counter. Concentrations of the compounds of this invention varying from 5 to 20 pg/ml were found to provoke a 50% inhibition of leukemic polymerase with a synthetic DNA template. Reaction templated by a synthetic RNA template (poly rA.rU) were even more susceptible.

Representative compounds of this invention in experiments carried out with native template on normal and tumor cells polymerase showed a higher susceptibility of the tumor enzymes to the tested compounds.

Other biological characteristics displayed by the new rifamycin derivatives include inhibition of focus formation on mouse, rat and human cells by the Moloney and Kirsten strain of murine sarcoma virus; selective inhibition of virus production by already transformed mouse and human cells; detection of revertant cells using the murine sarcoma virus-transformed non-producer mouse and rat cell systems. The rifamycin compounds of the present invention have confirmed their selective toxicity for virus-transformed cells of mouse, rat and human origin when tested for colony-forming ability.

In studies to determine the effect of the compounds in inhibiting focus formation by Moloney sarcoma virus on BALE/3T3 tissue cultures, the following procedure is employed.

BALE/3T3 cell culture are grown in 250 ml. plastic flasks in growth medium consisting of Eagles minimal essential medium with 10% fetal bovine serum. Cell counts are made with a Coulter counter after suspending the cells with trypsin-EDTA and diluting in growth medium. Moloney murine sarcoma virus, as a tumor homogenate is employed. It is passaged four times in a Swiss-derived high passage mouse embryo cell line and assayed for focus-forming units in BALE/3T3 cells. In conducting the studies, a modification of the method described by Hartley and Rowe, Proc. Nat. Acad. Sci., 55, 780 (1966) is used. In the present work, flasks are seeded with from l-2 X l cells in 25 ml. of growth medium and incubated at 37C. for 24 hours. Following the removal of fluids, virus at a predetermined number of focus forming units is introduced into 0.5 ml. of growth medium and allowed to adsorb on the monolaycr of cells for 90 minutes at 37C. Following this adsorption period, a predetermined quantity, usually at a dose rate of from about 5 to ug/ml of a rifamycin compound (previously dissolved in dimethyl sulfoxide at a concentration of 1 mg/ml) and carried in ml. of growth medium, is added and the cultures returned to the incubator. As a control, dimethyl sulfoxide alone in the growth medium is added to a separate culture. After three days incubation, the cultures are fluidchanged and foci of transformed cells counted at day seven.

In this same method, vesicular stomatitis virus, New Jersey serotype is studied. Methods used to grow and assay this virus have been described by Hackett et al., Virology, 31, 114 (1967). These properties indicate that these substances possess an effective inhibitory activity on virus-induced tumors in animals.

What is claimed is:

l. A rifamycin designated by the formula Me M HO Me 0H l MGOY' and 25-desacetyl and 16, 17; 18, 19; 28, 29-hexahydro derivatives thereof, wherein Me represents methyl group; X represents a CO, CS, C(:NH)- or an SO group; R represents hydrogen; R, represents l to 20 carbon atom alkyl, cyclopropyl, l to 20 carbon atom alkoxy, phenyl, naphthyl, substituted phenyl or substituted naphthyl wherein substituents are selected from 1 to 6 carbon lower alkyl, 3 to 6 carbon lower alk'enyl, 3 to 10 carbon cycloalkyl, phenyl, amino, 1 to 6 carbon lower alkanoylamino, hydroxyamino, monoand dilower alkylamino, cyano, halo, nitro, l to 6 carbon lower alltoxy, methylenedioxy, sulfo, carboxy, carbamyl and sulfonamido; a2 to 6 carbon alkyl group substituted with phenyl, substituted phenyl, naphthyl, or substituted naphthyl, as defined above; NR R wherein R and R independently designate hydrogen, C -C lower alkyl, C -C lower alkenyl, nitro, anilino, phenyl, o-tolyl, m-chlorophenyl or 3-fluoro-4-methylphenyl; CONl-l-N=CH-A or (R )CONH-N=CHA wherein R is methylene, ethylene, cyclohexylene, or phenylene and A represents the rifamycin SV group:

5 or the corresponding 25-desacetyl and l6, 17; 18, 19; 28, 29-hexahydro derivative thereof; and where R and R, taken together with the adjacent N-X-group designate 1,2,3,4-tetrahydro-3-oxo-2-isoquinolinyl or its l-oxo isomer, l-oxo-2-isoindolyl or I,3-dioxo-2- isoindolinyl.

UNITED STATES PATENT oTTTTJE CERTEFMIATE (Tl CQRRECTWN PATENT NO. I 3,865,812

DATE I February ll, 1975 WVENTOWS) Renato Cricchio and Giancarlo Lancini it is certn'leu mat error appears n The abovesdentified patent and that said Letters Patent are hem-y c0.':'ected as shown below Column 1, between lines 7 and 20, the formula should be identified as (I) Column 7, lines 35 and 36 should be del (They are a repetition of the footnote in Table I.)

Column 8, line 35, "TABLE II" should read TABLE II Cont.

Column 9, the fourth "H" should be deleted from under column R;

and,

Column 9, under column R, across from (CH CH (the 13th 218' 3 item under column R there should be shown an H.

Column ll, line 26, "mineral" should read minimal Column 13, line 52, "At template" should read As template @igned and Sealed this twenty-second D3) 0f July 1975 [SEAL] A ttest:

RUTH C. MASON C. MARSHALL DANN Am'sling Officer Commissioner of Parents and Trademarks 

1. A RIFAMYCIN DESIGNATED BY THE FORMULA 